The spectral properties of two block copolymers were investigated, based on the fluorene-EDOT (FEDOT) segment linked either to fluorene-thiophene (FTh) or to fluorenebenzothiadiazole (FBz) units, in an alternated fashion. Experimental data revealed that in the first material, each block keeps the spectral absorption region observed in the individual copolymers, while in the other structure new spectral characteristics were observed, as compared with each individual segment. In order to elucidate this behavior, theoretical calculations using density functional theory methods were performed. The block copolymers were reduced to a minimal representative model and the following structures were modeled: (FEDOT)(2), (FBz)(2) e (FTh)(2) relative to the alternated segments and (FEDOT)(2)-(FBz)(2) and (FEDOT)(2)-(FTh)(2) as mini-blocks for the block copolymers. The theoretical results showed good agreement with experimental data and used to interpret the differences in electronic behavior of the block copolymers and their correlation with the observed photophysical behavior. (C) 2016 Wiley Periodicals, Inc.